Steel casting mold insert

ABSTRACT

An insert for steel casting molds which consists of four individual heat-insulating plates. These plates are reinforced with steel sheets or rods on their sides facing the mold walls. When the molds are filled with liquid steel, the reinforcements fuse with the ingot upon cooling, and the insert leaves the mold together therewith. The insert remains on the ingot throughout reheating in a furnace prior to rolling and is discarded only in the roller mill as scrap. The device and the process of using the same reduce segregation and cavitation in the ingot, also considerably reduce scrap formation and lengthen the working life of the molds.

United States Patent 172] Inventors l-lelmut Kobusch Duisburg-Mundelheim; Walter Pfaff, Dusiburg-Huttenheim; Arnold Pfeiffer, Duisburg-Huckingen,

Germany [21 Appl. No. 687,547

[22] Filed Dec. 4, 1967 [45] Patented Feb. 9, 1971 [73] Assignee Mannesmann Aktiengesellschatt Dusseldorf, Germany [32] Priority Dec. 20, 1966 [3 3] Germany [54] STEEL CASTING MOLD INSERT Primary Examiner-.1 Spencer Overholser Assistant ExaminerJohn E. Roethel Attorney-Marmorek & Bierman ABSTRACT: An insert for steel casting molds which consists of four individual heat-insulating plates. These plates are reinforced with steel sheets or rods on their sides facing the mold walls. When the molds are filled with liquid steel, the reinforcements fuse with the ingot upon cooling, and the insert leaves the mold together therewith. The insert remains on the ingot throughout reheating in a furnace prior to rolling and is discarded only in the roller mill as scrap. The device and the process of using the same reduce segregation and cavitation in the ingot, also considerably reduce scrap formation and lengthen the working life of the molds.

1 Claim, 2 Drawing Figs.

[52] US. Cl 249/198, 249/106, 249/201 [51] lnt.Cl 322d 7/10 [50] Field of Search 249/ 106, 197, 202

PATENTED FEB 91971 Inventors. HELHIIT KOBuScH WHLTER PFMEF mum. PFHFFER STEEL CASTING MOLD INSERT The invention relates to an insertfor ingot molds and similar casting molds which consists of thin, heat-insulating plates which are detachably hung into the upper part of the mold. The device is particularly applicable for pouring and casting of killed steels.

A cavity or piping forms in the top end of the ingot when killed steels solidify. These cavities extend into the interior of the pig or ingot to a greater or lesser extent and fuse only partially during rolling. Therefore, a certain amount of scrap collects in the rolling mill which depends on the size of the piping. In order to obtain a dense ingot top end, the upper part of the mold is lined with heat-insulating plates which are suspended in the mold and rigidly connected thereto, as described, e.g., in German Patent 1,184,462. Thereby, the top of the ingot is kept in liquid state for a longer time than the lower end during solidification of the liquid steel. Thus, liquid steel can flow into the portion which had already solidified. It is necessary to keep the ingot head liquid for a prolonged period of time when heavy ingots are poured in order to carry off the large amounts of heat. Because the heat-insulating insert is removed together with the mold, the ingot must remain in the mold for a long time. This leads to an increased and undesirable segregation or liquation of carbon, sulfur and phosphorous within the head.

A procedure is known to decrease the piping formation, disclosed in German Patent 623,61 l, wherein the unlined mold is removed at an early stage, and the ingot is covered by a refractory cap. This is designed to keep the ingot top hot while accelerating cooling of the lower end. However, in this method the lack of heat insulation in the upper part of the mold entails carrying off of so much heat that an edge zone or casing forms on the ingot and simultaneously a cavity which is far inside the interior. Even an ensuing accelerated cooling of the ingot bottom while simultaneously keeping the top end hot, does not reverse the characteristic piping formation.

It now has surprisingly been found and is an object of the invention that cavity formation and liquation or segregation can be suppressed when, under continuous curbing of the heat removal in the ingot top, the mold is. removed at an early stage. I

It is another object of the invention to construct a mold provided with a heat-insulating zone in such a manner that the heat elimination remains curbed in the ingot top even after removal of the mold.

According to the invention, this is accomplished by detachably inserting in the mold an insert whose heat'insulating refractory plates are reinforced on the sides facing the mold wall, and a portion of the reinforcement protrudes into the mold interior. The reinforcement thereby protrudes beyond the lower edges of the plates and/or is fastened to the plates by means of metal pins which penetrate the plates. Both these measures can be applied severally or jointly. For instance, the reinforcement may be a steel sheet of 0.5 to L5 mm. thickness and may furthermore be integrally connectedto the plate surface or simply rest upon it. In such a mold the rising liquid steel fuses'with the reinforcement thus fastening the insert to the poured ingot. After severing the connection between insert and mold, the mold' can thus be removed without the insert. This has not been feasible with the molds hitherto known.

The invention now will be more fully explained with reference to the accompanying drawings and a preferred embodiment illustrated thereby. However, it should be understood that drawings and examples are given merely by way Referring now to these drawings, a smoothbore steel mill mold is shown as 1. In the upper part of mold l, the insert according to the invention is suspended. The insert may be disposed at a selected height of the mold, depending on the desired weight of the ingot. This insert consists of four individual refractory heat-insulating plates 2 to which metal strips 3 are fastened. These strips 3 are provided with holes at different height. Rods 4 are inserted into and through these holes and rest on the upper mold surface. Thereby, the insert is kept at the desired height. Wedges 5, made of like material as plates 2, hold the insert in place in mold I.

Plates 2 carry reinforcements 6 which impart sufficient strength even after pouring. These reinforcements 6 are of sheet steel of 0.5-1.5 mm. thickness and are fastened to the plate surfaces facing the mold wall. This is accomplished by means of pins 7 which are urged through the steel sheet and the plates.

In another embodiment of the invention, the reinforcements 6 are in the shape of rods which are integrally connected to the plates 2. The reinforcements extends by a few centimeters beyond the lower edge of the plates so that a portion of the reinforcement protrudes into the interior of the mold. Moreover, the pins 7 extend beyond the free surfaces of plates 3. However, it suffices if either the pins extend or the reinforcement protrudes. The extending portion of the reinforcement fuses with the rising liquid steeland thus fastens the insert to the poured ingot.

When the steel has solidified in the mold to such anextent that the ingot just separates from the mold wall and its core is still liquid, the mold is removed while the insert adheres to the ingot. After cooling, ingot and insert are heated to the temperature required for rolling in a vertical ingot furnace or pit furnace. The insert does not fall off in the furnace since it is fused to the ingot. Thus, the danger is averted that a liquid slag forms on the bottom of the furnace together with the scale. The mold insert is separated from the ingot only in the rolling mill. Because the surface of the-piece tobe rolled precedes its center upon rolling, the reinforcement sheet is pushed ahead so far that it reaches the portion of the ingot which is cut off as scrap.

When the ingot cools on the air, solidification of the lower part proceeds faster than in the mold. From the continuedly heat-insulated ingot head, liquid steel flows in which is rapidly consumed due to the accelerated cooling of the lower ingot part. This effects a decrease in the cavity formation and lesser liquation or segregation. Moreover, the volumeof the ingot head required for the production of a dense ingot can be reduced. All these factors result in a reduction of the scrap obtained in the rolling mill. The mold is removed at an early stage and accepts less heat than customary during solidification of the ingot. The lower thermal demand results in a longer working life of the molds. All these advantages are unattainable with molds hitherto known.

The molds provided with inserts according to the invention are successfully employed for casting of steels which are sensitive to heat cracking. Ingots made from such steels must be put into the ingot furnace at temperatures exceeding 900 C. In order to maintain these temperature limits, the conventional molds, especially on casting of heavy ingots, must be removed early enough, and the ingots charged rapidly enough, that the ingot head still is liquid when the ingot again is heated externally. Thereby, pronounced segregation occurs. According to the invention, the ingots, after removal of the mold, are cooled in the air for a short time until they have attained the required surface temperature. They then are transported in heat-insulated carts or dollies to the ingot furnace and installed therein. The ingot core, in this method, has solidified prior to the transport step so that no appreciable segregation occurs.

We claim:

1. A removable insert, for use in connection with a walled steel casting mold, comprising in combination:

'l. a plurality of heat-insulating plates. each disposed sub-' stantially parallel to a wall of said mold;

insert and mold;

4. connecting pieces disposed between said plates closing the sides of the insert; and

5. means operable for suspending the insert in the mold at a predetermined depth. 

1. A removable insert, for use in connection with a walled steel casting mold, comprising in combination:
 1. a plurality of heat-insulating plates each disposed substantially parallel to a wall of said mold;
 2. a steel reinforcement sheet of substantially .5 to 1.5 mm. thickness connected to each plate at the side facing the mold wall and extending axially into the interior of the mold;
 3. at least one pin connecting said steel reinforcement sheet to said plate and extending radially into the interior of the insert and mold;
 4. connecting pieces disposed between said plates closing the sides of the insert; and
 5. means operable for suspending the insert in the mold at a predetermined depth.
 2. a steel reinforcement sheet of substantially .5 to 1.5 mm. thickness connected to each plate at the side facing the mold wall and extending axially into the interior of the mold;
 3. at least one pin connecting said steel reinforcement sheet to said plate and extending radially into the interior of the insert and mold;
 4. connecting pieces disposed between said plates closing the sides of the insert; and
 5. means operable for suspending the insert in the mold at a predetermined depth. 